ANIMAL PEDIGREES. 131 



it shall not on one hand mean barren hypothesis, or 

 degenerate into a mere truism on the other. 



In his numerous investigations, Prof. Haeckel takes 

 up the strong ground, that the germ is an epitomy of 

 the history of descent; or more explicitly, that the 

 forms through which an organism passes from the 

 ovum to development is a compressed representation 

 of the forms through which the ancestors of that 

 organism have passed from its earliest period to the 

 present time. 



This hypothesis had its origin in the sagacious fore- 

 shadowings of Dollinger and Von Baer. 



An unbroken succession of animals has been repre- 

 sented by the formula A, B, C, to Z ; but, as links may 

 be lost or unknown in the sequence, the recognised 

 order may in reality be A, B, D, F, to Z. These gaps 

 in the ancestral chain may, however, be theoretically 

 bridged over, through considerations based on com- 

 parative anatomy and embryology, and thus the series 

 might become as A, B, A, D, 0, F. In this way 

 Prof. Balfour shows how these missing links may 

 be shadowed forth by the ontogenic history of B and 

 I) ; and this might lead to a more or less correct repre- 

 sentation of the tribal sequence. 



Formerly it was believed that all the parts to be 

 found in the adult animal were really included in the 

 embryo ; that they were in a certain manner wrapped 

 together, and that the passage from infancy to age 

 was a real growth ; but a new light appeared in Leu- 

 wenhoeck's important discovery of the spermatozoon. 

 The explanation then offered, however, did not really 

 advance a knowledge of the subject ; or, at least, the 

 general belief then was that each sperm-cell contained 

 the living individual in miniature, and that the ovum 

 merely acted as a nidus for its development. 



The vast majority, doubtless, are guided and live up 

 to the lights of their age. It is reserved for the re- 

 latively few to shake themselves clear of current 

 prejudices, and by their far-sighted originality to direct 



